Einstein rejected Newton's emission theory of light because he "expected a viable theory of light, electricity and magnetism to be a field theory":

http://www.pitt.edu/~jdnorton/papers/companion.pdf
John Norton: "Einstein's second postulate, the light postulate, asserts that "light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body." Einstein gave no justification for this postulate in the introduction to his paper. Its strongest justification came from Maxwell's electrodynamics. That theory had identified light with waves propagating in an electromagnetic field and concluded that just one speed was possible for them in empty space, c = 300,000 km/sec, no matter what the motion of the emitter. (...) Einstein could not see how to formulate a fully relativistic electrodynamics merely using his new device of field transformations. So he considered the possibility of modifying Maxwell's electrodynamics in order to bring it into accord with an emission theory of light, such as Newton had originally conceived. There was some inevitability in these attempts, as long as he held to classical (Galilean) kinematics. Imagine that some emitter sends out a light beam at c. According to this kinematics, an observer who moves past at v in the opposite direction, will see the emitter moving at v and the light emitted at c+v. This last fact is the defining characteristic of an emission theory of light: the velocity of the emitter is added vectorially to the velocity of light emitted. (...) If an emission theory can be formulated as a field theory, it would seem to be unable to determine the future course of processes from their state in the present. As long as Einstein expected a viable theory of light, electricity and magnetism to be a field theory, these sorts of objections would render an emission theory of light inadmissible."

In 1954 (perhaps even earlier) Einstein realized that the field concept (more precisely, his 1905 false constant-speed-of-light postulate) had killed physics:

http://www.perimeterinstitute.ca/pdf...09145525ca.pdf
Albert Einstein (1954): "I consider it entirely possible that physics cannot be based upon the field concept, that is on continuous structures. Then nothing will remain of my whole castle in the air, including the theory of gravitation, but also nothing of the rest of contemporary physics."

Here is the genius who knew how to build "a viable theory of light, electricity and magnetism" without killing physics:

http://ritz-btr.narod.ru/martinez2004pip6.pdf
Alberto Martinez: "In sum, Einstein rejected the emission hypothesis prior to 1905 not because of any direct empirical evidence against it, but because it seemed to involve too many theoretical and mathematical complications.. By contrast, Ritz was impressed by the lack of empirical evidence against the emission hypothesis, and he was not deterred by the mathematical difficulties it involved. It seemed to Ritz far more reasonable to assume, in the interest of the "economy" of scientific concepts, that the speed of light depends on the speed of its source, like any other projectile, rather than to assume or believe, with Einstein, that its speed is independent of the motion of its source even though it is not a wave in a medium; that nothing can go faster than light; that the length and mass of any body varies with its velocity; that there exist no rigid bodies; that duration and simultaneity are relative concepts; that the basic parallelogram law for the addition of velocities is not exactly valid; and so forth. Ritz commented that "it is a curious thing, worthy of remark, that only a few years ago one would have thought it sufficient to refute a theory to show that it entails even one or another of these consequences..." (...) Two months after Ritz's death, in September 1909, his exchange with Einstein barely echoed at a meeting of the Deutsche Naturforscher und Ärtze in Salzburg, where Einstein delivered a lecture elaborating his views on the radiation problem but made no explicit reference to Ritz's views. Two years later, however, in November 1911, Paul Ehrenfest wrote a paper comparing Einstein's views on light propagation with those of Ritz. Ehrenfest noted that although both approaches involved a particulate description of light, Ritz's theory constituted a "real" emission theory (in the Newtonian sense), while Einstein's was more akin to the ether conception since it postulated that the velocity of light is independent of the velocity of its source. (...) Ritz's emission theory garnered hardly any supporters, at least none who would develop it or express support for it in print. As noted above, in 1911, two years after Ritz's death, Ehrenfest wrote a paper contrasting Ritz's and Einstein's theories, to which Einstein responded in several letters, trying in vain to convince him that the emission hypothesis should be rejected. Then Ehrenfest became Lorentz's successor at Leiden, and in his inaugural lecture in December 1912, he argued dramatically for the need to decide between Lorentz's and Einstein's theories, on the one hand, and Ritz's on the other. After 1913, however, Ehrenfest no longer advocated Ritz's theory. Ehrenfest and Ritz had been close friends since their student days, Ehrenfest having admired Ritz immensely as his superior in physics and mathematics; but following Ritz's death, Einstein came to play that role, as he and Ehrenfest became close friends."

Pentcho Valev